Background

Back pain is one of the most common causes for disability in the working population. Some risk factors for back pain are well known, however little is known about factors uniquely associated with acute or chronic back pain.

This study aimed to elucidate patterns uniquely associated with acute or chronic back pain.

Methods

This study performed secondary analysis of data from the Welsh Health Survey 2012, a nationwide cross-sectional survey.

A multivariable analysis was carried out for risk factors found to be significantly associated with acute and chronic back pain.

Conclusion

Increased deprivation, female gender, and little exercise were uniquely associated with chronic back pain. These characteristics may help clinicians to intervene to prevent acute backpain resulting in chronic cases.

Back pain is a common and potentially disabling condition that can lead to reductions in quality of life, time off work and long-term disability. The Global Burden of Disease Study estimated the point prevalence of low back pain to be 9.4%, and reported low back pain to be the condition responsible for the most years lived with disability [1]. Back pain is one of the most common causes for disability in the working population, and severely impacts upon work productivity and absenteeism [1]. In the UK alone, almost 3.4 million working days were lost due to work-related back pain in 2016/17, that is 13.3% of all working days lost due to ill health [2]. Low back pain is the reason for one in every seven general practice consultations [3]. The associated health care cost and burden has been reported across health care systems worldwide [4, 5]. Hong et al. [6] found that the healthcare costs of patients suffering chronic low back pain (CLBP) were double those of matched controls without CLBP.

Chronic and acute back pain

Back pain is defined as acute when it has persisted for up to 6 weeks and sub-acute when it has persisted for up to 3 months [7]. Chronic back pain is defined as back pain that is present for more than 3 months [8] and is associated with patients receiving treatment [9, 10]. Acute back pain is often the result of actual or near tissue injury or sprain [7] and individuals with acute back pain are less likely to seek care or be referred for treatment [9, 10]. Chronic pain often persists even though the initial injury has healed [7]. These cases are more likely to be referred for treatment than the more acute cases that are commonly left untreated [9, 10].

Risk factors

There is good evidence for an association between increasing age and obesity (BMI > 30) and risk of back pain [4, 11–21] and that obesity is a strong predictor of disability caused by back pain [20, 22, 23]. It is also known that the prevalence and severity of back pain is higher where there is greater deprivation [4, 12, 14–16, 19–21, 24–28]. There is conflicting evidence on the effect of physical activity (PA) on back pain. Heneweer et al. [13] suggested a U-shaped dose-response relationship between PA and back pain. Other studies have found that physical inactivity is associated with a significant increase in risk of back pain [17, 22]. There is some evidence suggesting that females have a greater risk of back pain, [4, 11–21, 24] however a recent global study reported this varied by region [1].

There is limited evidence that job demands including lifting and twisting [13, 20, 26, 29]; ethnicity [18, 24]; genetic factors [14]; and mental health comorbidities [4, 14, 22, 26] are all associated with higher risk of back pain. The varying level of evidence, available literature and the lack of a standardised definition of back pain make definitive conclusions challenging [30, 31].

Aim and objectives

This study aimed to elucidate patterns uniquely associated with acute or chronic back pain. Differentiating between the two is challenging in clinical practice. Identifying risk factors associated with the pattern may help clinicians differentiate between the two conditions, manage them more appropriately and ultimately help to improve patient outcomes. In addition this could enable targeting of those at greatest risk for prevention through e.g. workplace modification strategies.

Study design

We used a population based cross-sectional survey (The Welsh Health Survey 2012). The survey collected information on health status, illnesses, lifestyle and health service use in the general population. The sampling frame includes 99% of all private households in Wales. A sample of 14,775 households were drawn, stratified by geographical area. To achieve the aim of at least 600 interviews per geographical area, a minimum of 575 households were sampled in each geographical area. Household data were collected by enumerator from each adult aged 16 years or older. Further details about collection of data can be found on the Welsh Health Survey 2013 (WHS) [32].

Outcomes

Primary outcomes in this study were:

a)

Acute back pain (episodes of untreated backache in the last 12 months) [9, 10]

Data analysis

An a priori statistical analysis plan was followed (available on request). Descriptive statistics tabulated demographic and risk factors, for acute and chronic back pain, and counts were presented. Crude logistic regression models were fitted to each risk factor and odds ratios (ORs) were presented with 95% confidence intervals (95% CI) and P-values. A multivariable logistic regression model with a forward stepping approach where a likelihood ratio test (LRT) of sequential nested models, was used to determine parsimonious independent associations with the covariates (p < 0.01). The final analyses were inclusive of all risk factors from either of the analyses. The analysis was adjusted for the clustered nature of the respondents within geographical areas within the UK, by estimating inflated standard errors using the robust cluster estimators of the variances. Stata 13 was used for all analyses.

There were 19,282 eligible adults who were invited in the WHS 2013, and 15,007 were included in the analysis. The response rate was higher among women (83.1%) than men (79.4%), as well as among older individuals than younger individuals (70.3% for 16–24 years, 75.6% for 25–44 years, 85.1% for 45–64 years, 88.9% for 65 years and older). There was less than 5% missing data for any included variable.

The prevalence of acute back pain was 31.5% and the prevalence of chronic back pain was 13.4% (Table 1). The prevalence of reported acute and chronic back pain combined was 39.1%.

Table 1

Numbers and proportions of acute and chronic back pain across all covariates

Acute back pain

Chronic back pain

All back pain

Total

Pain (%)

Total

Pain (%)

Total

Pain (%)

Total

14,359

4519 (31.5%)

14,351

1772 (13.4%)

14,100

5520 (39.1%)

Deprivation (WIMD quintile)

14,359

14,351

14,100

Least deprived

2839

892 (31.42)

2859

248 (8.67)

1029

1029, (36.65)

2

3065

994 (32.43)

3053

347 (11.37)

1207

1207, (40.07)

3

3275

1053 (32.15)

3309

409 (12.36)

1275

1275, (47.05)

4

2762

866 (31.35)

2745

381 (13.88)

1072

1072, (45.79)

Most deprived

2418

714 (29.53)

2385

387 (16,23)

2529

2529, (108.03)

Age (years)

14,359

14,351

16–24

1718

387 (22.53)

1752

46 (2.63)

410

410, (24.05)

25–44

3830

1264 (33.84)

3879

275 (7.09)

1421

1421, (37.25)

45–64

4963

1731 (34.88)

4974

709 (14.25)

2144

2144, (43.76)

65+

3848

1137 (29.55)

3746

742 (19.81)

1545

1545, (41.97)

Gender

14,359

14,351

Female

7699

2480 (32.21)

7667

1084 (14.14)

3098

3098, (41.05)

Male

6660

2039 (30.62)

6684

688 (10.29)

2422

2422, (36.96)

Educational attainment

13,398

13,424

No qualification

2643

752 (28.45)

2573

573 (22.27)

1077

1077, (42.27)

Other qualification

8367

2731 (32.64)

8443

883 (10.46)

3231

3231, (39.01)

Degree Equivalent and above

2388

774 (32.41)

2408

136 (5.65)

856

856, (36.03)

Occupational status (NS-SEC)

13,959

13,936

Managerial and Professional occupations

5170

1605 (31.04)

5228

461 (8.82)

1868

1868, (36.52)

Intermediate occupations

2853

964 (33.79)

2834

330 (11.64)

1143

1143, (40.88)

Routine and manual occupations

5569

1718 (30.85)

5524

883 (15.98)

2217

2217, (40.74)

Never worked and long-term unemployed

357

104 (29.13)

350

65 (18.57)

143

143, (41.81)

BMIa

13,387

13,391

Less than 18.5

281

59 (21.00)

284

21 (7.39)

71

71, (26.01)

18.5 to under 25

5176

1498 (28.94)

5213

490 (9.40)

1778

1778, (34.88)

25 to under 30

4878

1604 (32.88)

4873

594 (12.19)

1943

1943, (40.45)

30 and over

3052

1073 (35.16)

3021

550 (18.21)

1386

1386, (46.31)

Mental Health (SF-36 mental health score)

14,359

14,351

Higher than average (> 50)b

8803

2421 (27.50)

8862

632 (7.13)

2783

2783, (32.15)

Lower than average (< 50)c

5556

2098 (37.76)

5489

1140 (20.77)

2737

2737, (50.28)

Depression

13,840

14,165

Yes

1257

488 (38.82)

1183

403 (34.07)

717

717, (59.7)

No

12,583

3832 (30.45)

12,982

1204 (9.27)

4519

4519, (35.85)

Anxiety

13,776

14,124

Yes

1025

392 (38.24)

959

315 (32.85)

568

568, (58.32)

No

12,751

3904 (30.62)

13,156

1252 (9.52)

4624

4624, (36.16)

Exercise

14,136

14,139

Meeting PA guidelinesd

4106

1291 (31.44)

4156

269 (6.47)

1432

1432, (35.33)

Not meeting guidelines

10,030

3164 (31.55)

9983

1451 (14.53)

4001

4001, (40.64)

aBody mass index

bMental health score above the average of the general population

cMental health score below the average of the general population

dMeeting physical activity guidelines of 30 min of light to moderate exercise on at least 5 days of the week

The study aimed to describe a pattern of acute and chronic back pain and examine possible risk factors in order to elucidate differences between the sub-types of back pain. We found that increasing age, higher BMI, better educational attainment and poorer mental health were independently associated with both acute and chronic back pain. However, we also found that increasing WIMD quintile (i.e., increasing deprivation), female gender, and exercising less than 2 days per week were uniquely associated with chronic back pain.

This is the first population-based study to compare independent associations for acute and chronic back pain. The strength was larger for all of the associations for chronic back pain and the associations showed a diluted effect in acute back pain in most of the covariates.

Comparison with existing literature

Educational attainment had the opposite effect on acute back pain compared to chronic back pain, and higher educational attainment was significantly associated with increased odds of acute back pain. Riskowski [33] reported a similar finding in a cross-sectional survey conducted in the U.S., in which they found that chronic back pain was more common in individuals of lower socioeconomic position and that acute back pain was more common in individuals of higher socioeconomic positions. Riskowski suggests that these unusual findings could be related to changes in socioeconomic positions over time as acute pain becomes chronic [33]. Assuming that untreated backache represents acute cases and treated back pain represents chronic cases similar suggestions might be made for this study, as educational attainment is an important marker for socioeconomic status and deprivation. Definitive explanations of these findings are difficult, although speculative suggestions can be made that cases of acute back pain in those with higher educational attainment are less likely to become chronic because of better knowledge of self-regulation or coping strategies in addition to this group having in general better means. This would result in most back pain cases in those with higher educational attainment being acute and not becoming chronic. We found obesity (BMI > 30) to be independently associated with chronic back pain, this is in line with previous studies [4, 11–21]. Fransen et al. (2002) found obesity to be a significant predictor of chronicity in individuals receiving compensation for working days lost due to acute back pain [34].

A recent systematic review found that stratified programmes were effective in preventing the development of chronic back pain. Those classified at low risk of developing chronic back pain benefited from simple educational messages while those classified at medium or high risk benefited from a combination of reactivation programmes, exercise and cognitive-behavioural interventions. We have identified factors independently associated with chronic back pain only. This may help to determine the risk of patients developing chronic back pain, and in turn determine a suitable prevention intervention [35].

Our findings in general are in line with previous studies however it is the first in the UK to distinguish between acute and chronic back pain.

Strengths and limitations

This is the first population-based study of back pain in the UK, and the first to differentiate between acute and chronic back pain. The reported results cannot infer causality due to the nature of the study design. Multivariable analyses controlled for known confounders, however this doesn’t include the unknown confounders, i.e. work demands, chronic stress and genetic factors. There is a limitation in the measures for chronic and acute back pain used in this study. The evidence suggests that treated cases are likely to represent chronic cases and untreated cases are likely to represent acute cases [9, 10]. However, we anticipate that some cases may be misclassified, as acute back pain may sometimes be treated with for example, anti-inflammatories.

There is debate over these definitions and this is unlikely to be universal. Potential biases affecting the study include selection bias and reporting bias. We cannot ignore the possibility of reverse causality. Given the weaknesses, caution is needed when interpreting these findings, however, this study gives a clue about the difference in risk factors between acute and chronic back pain.

Chronic back pain is a considerable public health concern and risk factors for acute and chronic back pain are different. This study has identified factors associated with chronic back pain that are not associated with acute back pain. This information may help clinicians to intervene to prevent acute back pain resulting in chronic cases. More emphasis should be put on service for those in deprived areas. In addition this information can help target groups and individuals for preventive measures.

Longitudinal cohort studies are needed to make conclusions about causality regarding risk factors of back pain and to distinguish successfully between cases that progress form acute to chronic. In addition further analysis of long-term cohort studies are needed to investigate the effect of light exercise on chronic back pain as a suggested means of self-management.

Acknowledgements

The authors would like to thank the team at the Health statistics and analysis unit, Welsh Government, who provided the data used in this analysis.

Funding

We acknowledge the support of the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London (B. C.). The funding bodies were not party to any part of the research, analysis, interpretation, or dissemination.

Availability of data and materials

The data that support the findings of this study are available from The Welsh Government (The Welsh Health Survey) but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are however available from the authors upon reasonable request and with permission of Welsh government.

Authors’ contributions

SJ and BC carried out the data collection and analysis and were major contributors in writing the manuscript. KT and HA were contributors in writing and reviewing the manuscript and all authors read and approved the final manuscript.

Ethics approval and consent to participate

The data used in this study was obtained from a cross-sectional nationwide survey and data were anonymised. Ethical approval was included in Welsh Health Survey, and a local ethics committee ruled that participants were not required to be additionally consented for this study.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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